Not applicable.
Not applicable.
1. Field of the Invention
The present invention relates, generally, to testing apparatus and methods. More particularly, the invention relates to electromechanical testing apparatus for measuring the spring rate of torsion bars used on automobiles.
2. Background Information
Balancing a car optimizes performance, particularly the cornering characteristics of a racing class automobile. The traction, adherence or grip between the tires and the track at each end of a car is proportional to the percentage of the weight at that end of the car. A car""s grip is optimized when both the front tires and the rear tires begin to slide at the same time and at the same rate, resulting in the car having responsive, near-neutral handling characteristics. However, if the front tires slide first, the car tends to understeer and slide off of the track, and if the rear tires slide first, the car tends to oversteer and spin.
Numerous factors contribute to the near-neutral handling characteristics of a balanced car, including tires, wheel alignment, suspension, weight distribution, center of gravity and aerodynamics. A properly suspended car has more braking and acceleration control when the car is moving in a straight line and more steering control when the car is maneuvering around comers.
A torsion bar suspension controls the lateral transfer of weight during cornering without degrading other aspects of the ride quality. A torsion bar suspension exerts resistance against up and down movement by using the flexible lengthwise twisting of a steel bar or tube to provide spring action, rather than the flexing action of a leaf spring or the compressing-and-extending action of a coil spring. One end of the bar is fixed solidly to a part of the frame behind the wheel, and the other end of the bar is attached to the lower control arm which rises and falls with wheel movement. The bar twists and absorbs shocks when the wheel rises and falls due to pressure and untwists when the pressure is released.
Torsion bars function as torsion springs and generally provide a stiff suspension while a car negotiates corners. Torsion bars may be used as anti-sway bars to reduce body roll by keeping the car flatter in turns. The anti-sway bars transfer the pressure exerted on the outbound wheels and apply opposite pressure to the inbound wheels to apply weight more evenly to all four wheels, which helps the vehicle stay level with the load. Stiffer torsion bars transfer more weight to the outside wheel during cornering. A stiffer or thicker front torsion bar causes the front tires to slide more quickly and causes the car to understeer, and a softer or thinner front torsion bar causes the car to oversteer. A stiffer or thicker rear torsion bar causes the rear tires to slide more quickly and causes the car to oversteer and a softer or thinner torsion bar causes the car to understeer.
Torsion bars have a spring rate that identifies the amount of resistance that it provides against up and down movement. This spring rate may change over time and may change because of use. It is therefore desirable to be able to accurately measure the spring rate of torsion bars in order to calculate the resistant force, balance the car, and ultimately improve the handling characteristics of the car.
Applicants"" invention provides an apparatus and method for testing and measuring the spring rate of torsion bars which is believed to constitute an improvement over existing technology.
The present invention provides an apparatus for testing and measuring the spring rate of torsion bars, or torsion bar tester, which generally comprises a frame, a load cell attached to the frame, a connector movably supported by the frame, a torque arm connected to the connector, a force applicator connected to the frame and to the torque arm, and a force indicator. One end of a torsion bar is connected to the load cell and the other end of the torsion bar is connected to the connector. The force applicator is positioned between the frame and the torque arm, and applies a torque force to the torsion bar at the connector. The force indicator, preferably a digital display, accurately displays the torque force applied to the torsion bar as gauged by the load cell. An angle indicator may be used in conjunction with a potentiometer to measure the angular displacement of the torsion bar for an applied torque force. The torsion bar tester accommodates torsion bars within a wide range of lengths and diameters. Furthermore, the torsion bar tester can apply a torque force in either rotational direction to accommodate torsion bars that have been installed as part of a car""s suspension and have undergone a torque force in a particular rotational direction. Once a torque force has been applied to a torsion bar, it may be undesirable to apply a torque force in the other rotational direction. An angle indicator, preferably a digital display, accurately displays the angular displacement as the torsion bar is twisted up to 25 degrees in either direction.
The torsion bar tester accurately determines the true spring rate of a torsion bar without any effects of friction that could skew the results. The structural design of the torsion bar tester isolates the load cell on one side of the torsion bar while a torque force is applied to the other side. Additionally, the torsion bar tester minimizes slippage with the torsion bar when the torque force is applied.
The features, benefits and objects of this invention will become clear to those skilled in the art by reference to the following description, claims and drawings.